When it is desired to simultaneously display two video signals, A and B, on a single television screen, it has been common practice to extract, from the signals A and B, only those portions required and to display the desired portions on the same screen to form a single picture thereon. With this practice, if any desired portions of the two signals coincide, or lie in the same position in the picture frame, only one or the other of the two desired portions can be displayed on the screen. This situation can be rectified, if either of the two signals A and B are produced by a local television camera, by shifting the scene or subject being televised or by changing the camera angle or the position at which the camera is set. Alternatively, if both signals A and B are fixed signals, such as the ones from a video tape recorder, a film projection, a telop, or a fixed camera, either one of the two signals must be eliminated.
It is, therefore, an object of the present invention to provide a television picture special effects system which makes it possible to display any desired portion of a video signal in any desired position on the television screen without requiring an operation at the signal source.